JP2010055887A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery (a lithium ion battery or the like) having high durability even in high rate use. <P>SOLUTION: The secondary battery 20 includes: a wound electrode body 80; and a heat radiation member 70 arranged on the inside of the winding inner periphery. The heat radiation member 70 is configured such that heat is efficiently radiated in the central part in the winding axial direction of the electrode body 80 than both ends. Preferably, the heat radiation member 70 is made of a material having relative high heat conductivity, and includes a high heat conductive part 72 continuing from the central part in the axial direction of the electrode body 80 to at least one end of the heat radiation member 70 in the axial direction; and low heat conductive parts 74, 76 made of a material having lower heat conductivity than the high heat conductive part. The low heat conductive parts 74, 76 cover the high heat conductive part 72 in a portion of the outer surface facing the inner periphery of the electrode body 80 out of the heat radiation part 70, and expose the high heat conductive part 72 in a portion of other part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a secondary battery including an electrode body (winding electrode body) having a configuration in which positive and negative electrode sheets are wound.

  Lithium ion batteries, nickel metal hydride batteries and other secondary batteries (storage batteries) are becoming increasingly important as on-vehicle power supplies or personal computers and portable terminals. In particular, a lithium ion battery that is lightweight and obtains a high energy density is expected to be preferably used as a high-output power source mounted on a vehicle. As one of typical structures of such a secondary battery, a positive electrode sheet and a negative electrode sheet are typically provided with an electrode body (winding electrode body) having a configuration in which the positive electrode sheet and the negative electrode sheet are laminated and wound via a separator. There is. For example, Patent Documents 1 to 3 are cited as prior art documents relating to this type of secondary battery.

JP 2007-311274 A JP 2000-260474 A Japanese Patent Laid-Open No. 2001-313078

  By the way, some uses of the lithium ion battery are assumed to be used in a mode in which high rate discharge (rapid discharge) is performed. A lithium ion battery used as a power source for a vehicle (for example, a battery mounted on a hybrid vehicle using a battery and another power source having a different operating principle such as an internal combustion engine as a power source, Is used in the form of an assembled battery in which a plurality of batteries are connected in series.) Is a representative example of a lithium ion battery in which such a usage mode is assumed. However, even though conventional lithium ion batteries show relatively high durability for use at low rates (charging / discharging), performance degradation (increase in internal resistance) when used at high rates Etc.). When such performance deterioration occurs in any of a plurality of batteries (single cells) constituting the assembled battery, the performance of the assembled battery as a whole may be significantly reduced.

  Accordingly, an object of the present invention is to provide a secondary battery (for example, a lithium ion battery) that exhibits good durability even when used at a high rate. Another object of the present invention is to provide an assembled battery constructed by using a plurality of such secondary batteries and exhibiting good durability even when used at a high rate.

  When the present inventor performs high-rate charge / discharge on a secondary battery (for example, a lithium ion battery) including a wound electrode body, the center part of the electrode body compared to both ends in the winding axis direction. It has been found that since the temperature rise is large, a temperature difference (temperature deviation) occurs between the center and both ends. When such a temperature distribution exists, the battery reaction (current) is concentrated at a relatively high temperature location, and the deterioration of the location easily proceeds. As a result, the performance of the entire battery can be deteriorated faster than usual. . In addition, since the amount of heat generation increases at locations where battery reactions concentrate, the temperature difference once generated tends to fall into a vicious circle. Therefore, the present inventor has found a configuration that can effectively eliminate or alleviate such a temperature difference, and has completed the present invention.

A secondary battery (typically a lithium ion battery) provided by the present invention includes an electrode body on which positive and negative electrode sheets are wound, and an inner side (winding center portion) of the wound inner periphery of the electrode body. And a heat radiating member disposed. The heat dissipating member is configured to dissipate heat at the central portion of the electrode body in the winding axis direction more efficiently than both end portions.
According to the secondary battery having such a configuration, when the high rate is used, the temperature of the central part tends to be greatly increased compared to the both axial ends of the electrode body. By disposing the cooling member at the center of winding of the electrode body, it is possible to eliminate or alleviate an event in which a temperature difference occurs between the axial center and both ends of the electrode body. Thereby, the bias of the battery reaction in the battery and the promotion of partial deterioration (for example, increase in internal resistance) due to this can be prevented, and the durability of the battery against high rate use can be improved.

  In the present specification, the term “secondary battery” is a term that generally refers to an electricity storage device that can be repeatedly charged, such as a so-called storage battery such as a lithium ion battery, a nickel hydride battery, a nickel cadmium battery, and an electric double layer capacitor. Includes power storage elements.

  In a preferable aspect of the secondary battery disclosed herein, the heat dissipation member is made of a material having a relatively high thermal conductivity (that is, a material having a higher thermal conductivity than a low thermal conductivity portion described later, for example, a metal material). And a low thermal conductivity portion made of a material (for example, a resin material) having a lower thermal conductivity than the high thermal conductivity portion. The high heat conducting portion is continuous from a portion of the heat radiating member disposed at a central portion in the axial direction of the electrode body to at least one end of the heat radiating member in the axial direction. In addition, the low thermal conductivity portion is an outer surface of the heat dissipating member that faces the inner circumference of the electrode body (that is, a surface of a portion of the heat dissipating member that is disposed inside the electrode body, typically an electrode. A part of the surface of the portion around which the sheet is wound is provided so as to cover the high heat conduction part, and the other part is provided to expose the high heat conduction part. For example, the portion of the heat dissipating member that is disposed at the central portion in the axial direction of the electrode body is configured such that the ratio of the area where the high heat conductive portion is exposed is higher than the portion that is disposed at both ends. Is preferred. In the secondary battery having such a configuration, the heat at the central portion in the axial direction of the electrode body is efficiently radiated through the high heat conduction portion, while the heat radiation is suppressed by the low heat conduction portion covering the high heat conduction portion at both ends in the axial direction of the electrode body. Yes. Thereby, the temperature difference between the axially central portion and both end portions of the electrode body can be effectively eliminated or alleviated.

  As a preferable application target of the technology disclosed herein, a secondary battery (for example, a lithium ion battery) including an electrode body (that is, a flat electrode body) in which the electrode sheet is flatly wound can be given. The secondary battery having such a form is preferable because it is easy to realize good heat transfer from the electrode body to the heat radiating member on the flat surface of the electrode body (particularly the central portion of the flat surface). For example, the present invention can be applied to a secondary battery having a configuration in which the flat electrode body is accommodated in a flat rectangular container.

  Thus, in a preferable aspect of the secondary battery including the flat electrode body, the heat dissipation member is formed by laminating the high heat conduction portion and the low heat conduction portions disposed on both sides thereof in the thickness direction of the flat electrode body. It has the structure made. According to this aspect, the temperature difference between the axially central portion and both end portions of the electrode body can be effectively eliminated or alleviated by a heat dissipation member having a simple configuration. For example, a heat radiating member having a configuration in which a thin plate-like low heat conduction portion having an opening exposing the high heat conduction portion in a portion disposed in a central portion of the flat surface of the electrode body is laminated on both sides of the thin plate-like high heat conduction portion Can be preferably employed. According to the secondary battery including such a heat dissipating member, the temperature difference between the axially central portion and both end portions of the electrode body can be effectively eliminated or alleviated.

  Any of the secondary batteries (for example, lithium ion batteries) disclosed herein can exhibit good durability for use at a high rate as described above. It is suitable as a power source for a motor (electric motor) of a vehicle such as an automobile. Therefore, according to the present invention, there is provided a vehicle including any of the batteries disclosed herein (which may be in the form of an assembled battery in which a plurality of the batteries are connected).

  As a preferable application object of the technology disclosed herein, lithium ions that can be used in a charge / discharge cycle including a high-rate discharge of 50 A or more (for example, 50 A to 250 A), or even 100 A or more (for example, 100 A to 200 A). Batteries: Large capacity type with a theoretical capacity of 1 Ah or more (and 3 Ah or more), and used in a charge / discharge cycle including high-rate discharge of 10 C or more (for example, 10 C to 50 C) or 20 C or more (for example, 20 C to 40 C). Examples of lithium ion batteries such as lithium ion batteries, assembled batteries constructed using the lithium ion batteries (using the lithium ion batteries as single cells), and power supply systems including the assembled batteries .

  Moreover, as a preferable application object of the technology disclosed herein, the size when the electrode body is viewed from the side of the winding axis is 5 cm or more in the winding axis direction (the horizontal direction in FIG. 2 and the vertical direction in FIG. 9) ( A lithium ion battery that is typically 5 cm to 25 cm (for example, 7 cm to 20 cm), an assembled battery constructed using the battery as a single battery, and a power supply system including the assembled battery are exemplified. Thus, in a lithium ion battery having a relatively long (large) axial length of the electrode body, the temperature difference between the axial end portions and the central portion tends to be large, and thus the present invention is particularly significant.

  Further, the technology disclosed herein includes an electrode body in which a positive and negative electrode sheet and a separator are wound in a flat shape, and the electrode body is a size as viewed from the normal direction of the flat surface (the lateral direction of the winding axis). Is 5 cm or more in the winding axis direction (typically 5 cm to 25 cm, for example, 7 cm to 20 cm), and 5 cm or more in the width direction (vertical direction in FIG. 2, typically the height direction) (typically Can be preferably applied to a lithium ion battery that is 5 cm to 25 cm (for example, 7 cm to 20 cm), an assembled battery constructed using the battery as a single battery, and a power supply system including the assembled battery. In this way, the axial length of the electrode body is relatively long and wide (large, large size) lithium ion battery, because the temperature difference tends to be large between the axial end portions and the central portion, The significance of application of the present invention is particularly great.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following drawings, members / parts having the same action are described with the same reference numerals, and overlapping descriptions may be omitted or simplified.
Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, the configuration and manufacturing method of the positive electrode, the negative electrode, and the separator, the manufacturing method of the electrode body, and the construction of the assembled battery) The method and the method of mounting the battery on the vehicle, etc.) can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

<Embodiment 1>
A preferred embodiment in which the present invention is applied to a lithium ion battery including a flat wound electrode body will be described with reference to FIGS.
The lithium ion battery 20 according to the present embodiment includes a positive and negative electrode sheet (typically, a sheet-like electrode in which each positive and negative electrode current collector holds a positive and negative electrode active material), a sheet-like separator, A container having a shape (here, a flat rectangular parallelepiped shape, that is, a square shape) in which a flat wound electrode body 80 in which the electrode bodies 80 are stacked and wound together with an appropriate liquid electrolyte (electrolytic solution) is accommodated. 50. Here, as shown in FIGS. 2, 5, and 6, a heat radiating plate 70 is disposed on the inner side of the wound inner periphery of the electrode body 80 (that is, the wound center). The material which comprises the container 50 can be made into the same thing as what is used with a typical lithium ion battery, for example, and there is no restriction | limiting in particular. From the viewpoint of heat dissipation and the like, a metal (for example, aluminum) container 50 can be preferably used. From the upper surface of the container 50, a positive electrode terminal 60 and a negative electrode terminal 62 that are electrically connected to the positive electrode and the negative electrode of the electrode body 80, respectively, protrude.

Hereinafter, the structure of the heat radiating plate 70 and the wound electrode body 80 will be described in more detail.
3 and 4, the heat radiating plate 70 includes a generally rectangular metal plate (high heat conductive member) 72 and resin sheets 74 and 76 superimposed on both surfaces of the metal plate 72. Has been. In the resin sheets 74 and 76, the direction corresponding to the axial direction of the electrode body 80 (hereinafter, for convenience of explanation, the “direction corresponding to the axial direction of the electrode body 80” is also referred to as “axial direction for the heat dissipation plate 70 and its constituent members. The openings 74A and 76A are respectively provided in the center portion in the width direction and the center portion in the width direction. Central portions of both surfaces of the metal plate 72 are exposed portions 72A that are exposed to the outer surface of the heat radiating plate 70 through the openings 74A and 76A. On the other hand, the peripheral portions of both surfaces of the metal plate 72 are covered portions 72B whose surfaces are covered with the resin sheets 74 and 76 (that is, not exposed to the outside). Thus, the heat radiating plate 70 is configured such that the ratio of the exposed area of the metal plate 72 is higher in the central portion 5 in the axial direction than in the end portions 6 and 7. That is, in the cross section at the negative electrode side end portion 7 shown in FIG. 5 (the cross section at the positive electrode side end portion 6 is the same), both surfaces of the metal plate 72 are entirely covered portions 72B. 6, an exposed portion 72A occupying, for example, 10 to 90% (typically 30 to 70%) of the length in the width direction is formed in the center portion of the metal plate 72 in the width direction. Has been. As a modification, the resin sheets 74 and 76 cover only the end portions 6 and 7, and the both surfaces of the metal plate 72 are exposed over the entire length in the width direction at the central portion 5 of the heat radiating plate 70. Also good.
4, the metal plate 72 is continuous from the central portion 5 to both ends 70A and 70B in the axial direction and both ends 70C and 70D in the width direction of the heat radiating plate 70. Ends) 70A, B, C, and D are exposed on the outer surface of the heat dissipation plate 70.

The constituent material of the heat radiating plate 70 is not particularly limited as long as it shows a desired stability with respect to the electrolytic solution to be used and the battery reaction. For example, as the constituent material of the metal plate 72, aluminum and other metal materials that are lightweight and have high thermal conductivity can be preferably used. Moreover, as a constituent material of the resin sheets 74 and 76, lightweight and hard polypropylene and other synthetic resin materials can be preferably employed. A synthetic resin porous member may be used. For example, a porous polyolefin sheet that can also be used as a separator sheet can be used alone or in an overlapping manner so as to have a required thickness.
The thickness of the metal plate 72 can be, for example, about 0.02 mm to 10 mm, and a metal plate having a thickness of about 0.05 mm to 5 mm (for example, 0.5 mm to 2 mm) can be preferably used. If the thickness of the metal plate constituting the high heat conduction part is too large, the physique (thickness) and weight of the battery 20 tend to increase, and if the thickness of the metal plate is too small, the effect of reducing the temperature difference may be reduced. is there.
The thickness of the resin sheets 74 and 76 can be set to, for example, approximately 0.005 mm to 2 mm, and usually a resin sheet having a thickness of approximately 0.02 mm to 1 mm (for example, 0.05 mm to 0.5 mm) is preferably employed. obtain. If the thickness of the resin sheet constituting the low heat conduction part is too large, the physique (thickness) and weight of the battery 20 tend to increase, and if the thickness of the resin sheet is too small, the effect of reducing the temperature difference may be reduced. is there.
In addition, the constituent material and shape (thickness, shape of an opening part, etc.) of both the resin sheets 74 and 76 may be the same, or may differ. Usually, resin sheets 74 and 76 having the same shape and made of the same material are preferably used.

  As shown in FIG. 2, the electrode body 80 has a long sheet-like positive electrode 82 (hereinafter also referred to as “positive electrode sheet 82”) and a long sheet-like electrode, similarly to a wound electrode body of a normal lithium ion battery. A negative electrode 84 (hereinafter also referred to as “negative electrode sheet 84”) is laminated together with a total of two long sheet-like separators 86 (hereinafter also referred to as “separator sheets 86”), and the stacked sheets 82, 84, It can be made by winding 86 in the longitudinal direction. Here, when winding the stacked sheets 82, 84, 86 (hereinafter also referred to as “laminated sheet”), the heat radiating plate 70 is used as a core, and the laminated sheet is tightly wound around the periphery. The flat electrode body 80 in which the heat radiating plate 70 is disposed inside the wound inner periphery can be suitably manufactured. According to this method, the outer surface (both surfaces and outer peripheral ends 70C and 70D) of the heat radiating plate 70 and the inner periphery of the laminated sheet can be brought into better contact (with a wider area). By this, the installation effect of the heat radiating plate 70 (the effect of relaxing the temperature difference between the central portion and both end portions of the electrode body 80) can be exhibited better. As shown in FIGS. 5 and 6, the outer peripheral ends 70 </ b> C and 70 </ b> D of the heat dissipating plate 70 are rounded (typically R-shaped), so that the outer periphery of the heat dissipating plate 70 and the inner periphery of the laminated sheet are reduced. It can be brought into better contact. Thus, by providing the outer peripheral ends 70C and 70D with roundness, the contact stress between the heat radiation plate 70 and the laminated sheet can be relaxed (distributed) to prevent the laminated sheet from being damaged.

  Or after laminating | stacking a lamination sheet independently, you may insert the thermal radiation plate 70 inside the winding inner periphery. The laminated sheet may be wound in a flat shape, or may be formed in a flat shape by winding it once in a circular shape and then crushing it from the side direction (lateral direction with respect to the winding axis). According to such a method, although the adhesion between the width direction ends 70C and 70D and the heat radiating plate 70 tends to be lower than the method of winding a laminated sheet around the heat radiating plate 70, higher productivity can be realized. The effect is obtained. Further, by bringing both surfaces of the heat radiating plate 70 into close contact with the flat surface of the electrode body 80, the temperature difference between the center portion and both end portions of the electrode body 80 can be effectively reduced.

  In addition, the positive electrode sheet 82 and the negative electrode sheet 84 are wound in a state where they are overlapped with a slightly shifted position in the width direction of these long sheets. As a result, as shown in FIG. 2, one end in the width direction of the positive electrode sheet 82 is provided on one end and the other end in the winding axis direction of the wound electrode body 80. 82, a portion where the negative electrode active material layer forming portion 82, the negative electrode active material layer forming portion of the negative electrode sheet 84, and the separator sheet 86 are closely wound) and one end in the width direction of the negative electrode sheet 84 However, a portion protruding outward from the wound core portion 81 is formed. One end of each of the positive electrode terminal 60 and the negative electrode terminal 62 is connected to the protruding portion of the positive electrode (that is, the portion where the positive electrode active material layer is not formed) and the negative electrode protruding portion (that is, the portion where the negative electrode active material layer is not formed).

The material and member itself constituting the wound electrode body 80 may be the same as the electrode body of the conventional lithium ion battery, and are not particularly limited. For example, the positive electrode sheet 82 can be formed by applying a positive electrode active material layer for a lithium ion battery on a long positive electrode current collector. For the positive electrode current collector, an aluminum foil (this embodiment) or other metal foil suitable for the positive electrode can be suitably used. As the positive electrode active material, one type or two or more types of materials conventionally used in lithium ion batteries can be used without any particular limitation. As a preferred example, a lithium-nickel composite oxide (an oxide containing lithium and nickel as constituent metal elements, a part of nickel site (typically less than half) is other metal elements such as cobalt and aluminum. It is meant to include substituted ones, typically LiNiO ₂ ), lithium cobalt based composite oxide (typically LiCoO ₂ ), lithium manganese based composite oxide (typically LiMn ₂ O ₄ ). And lithium transition metal composite oxides. For example, a long aluminum foil having a thickness of about 5 μm to 20 μm (for example, 15 μm) is used as a current collector, and a positive electrode active material layer mainly composed of a lithium nickel-based composite oxide is formed on a predetermined region of the surface by a conventional method. A suitable positive electrode sheet 82 is obtained by forming.

  On the other hand, the negative electrode sheet 84 can be formed by providing a negative electrode active material layer for a lithium ion battery on a long negative electrode current collector. For the negative electrode current collector, a copper foil (this embodiment) or other metal foil suitable for the negative electrode can be suitably used. As the negative electrode active material, one type or two or more types of materials conventionally used in lithium ion batteries can be used without any particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon, lithium transition metal oxides (such as lithium titanium oxide), and lithium transition metal nitrides. For example, a long copper foil having a thickness of about 5 μm to 20 μm (for example, 10 μm) is used, and a negative electrode active material layer mainly composed of a carbon-based material (typically graphite) is formed on a predetermined region of the surface by a conventional method. By forming it, a suitable negative electrode sheet 84 is obtained.

  Moreover, as a suitable separator sheet 86 used between the positive / negative electrode sheets 82 and 84, what was comprised by the synthetic resin (for example, polyolefin, such as polyethylene and a polypropylene) is illustrated. For example, a porous separator sheet made of polyolefin resin and having a thickness of about 5 μm to 30 μm (for example, 25 μm) can be suitably used.

A flat wound electrode body 80 having a heat radiating plate 70 disposed on the inner periphery of the winding is accommodated in the container 50 so that the winding shaft lies sideways as shown in FIGS. A lithium ion battery 20 according to this embodiment can be constructed by injecting and sealing a non-aqueous electrolyte solution (not shown). As the electrolytic solution, for example, a nonaqueous solvent (such as a mixed solvent of diethyl carbonate and ethylene carbonate) containing an appropriate supporting salt (for example, a lithium salt such as LiPF ₆ ) in an appropriate amount (for example, a concentration of 1 M) is preferably used. be able to.

According to the lithium ion battery 20 having such a configuration, the central portion of the electrode body 80 can be radiated with higher efficiency than both ends by using the heat radiating plate 70. That is, in the portion of the heat radiating plate 70 disposed at the center in the axial direction and the center in the width direction of the electrode body 80, the metal plate 72 is exposed to the outside through the openings 74A and 76A as shown in FIG. Therefore, the heat of the electrode body 80 can be efficiently transmitted to the metal plate 72. In addition, since the metal plate 72 is continuous from the central portion to the outer peripheral ends 70A, B, C, and D of the heat radiating plate, the heat received from the electrode body 80 can be effectively dissipated to the outside. On the other hand, at both axial ends of the electrode body 80, as shown in FIG. 5, the surface of the metal plate 72 is covered with resin sheets 72 and 74 (the inner periphery of the electrode body 80 and the metal plate 72 are resin sheets). 72, 74), the heat of the electrode body 80 is less likely to be transmitted to the metal plate 72 compared to the central portion. That is, heat dissipation is suppressed at both axial ends of the electrode body 80 as compared to the central portion. Therefore, in the conventional configuration, the temperature at the central part in the axial direction of the electrode body tends to rise greatly compared to both ends (the temperature difference between the central part and both ends tends to become large). According to the battery 20 of the embodiment, the temperature difference between the axially central portion and both end portions of the electrode body 80 can be effectively reduced.
In FIG. 6, since the thickness of the resin sheets 72 and 74 is exaggerated, the inner periphery of the electrode body 80 and the surface of the metal plate 72 are separated from each other. Because of its small size, the inner periphery of the electrode body 80 is in close contact with the surface of the metal plate 72 through the openings 74A and 76A. Since the electrode body 80 is typically accommodated in the container 50 so that a certain amount of pressing force is applied in the thickness direction, the above-described close contact is better performed.

  In order to confirm the significance (necessity) of adopting such a configuration, a lithium ion battery having the same configuration as that of the present embodiment except that the heat radiating plate 70 is not provided is manufactured, and both ends and the central portion are formed by high-rate charge / discharge. The temperature difference that occurred during

  That is, lithium nickelate powder (positive electrode active material), acetylene black (conductive material), and carboxymethyl cellulose (CMC) are mixed with ion-exchanged water so that the mass ratio of these materials is 87: 10: 3. A material composition (positive electrode active material composition) was prepared. A long aluminum foil is used as the positive electrode current collector, and the positive electrode active material composition is striped on both sides of the current collector, leaving one end in the width direction (positive electrode protruding portion). And dried. After drying, the whole including the positive electrode current collector and the active material layers provided on both sides thereof was pressed to obtain a positive electrode sheet.

  Further, natural graphite (powder), styrene butadiene rubber (SBR), and CMC are mixed with ion-exchanged water so that the mass ratio of these materials becomes 98: 1: 1. Prepared). A long copper foil is used as the negative electrode current collector, and the negative electrode active material composition is striped on both sides of the current collector, leaving one end in the width direction (negative electrode protruding portion). And dried. After drying, the whole including the negative electrode current collector and the active material layers provided on both sides thereof was pressed to obtain a negative electrode sheet.

Two porous polyethylene sheets were used as the separator sheet. These separator sheets and the positive electrode sheet and the negative electrode sheet obtained above are laminated and wound in the longitudinal direction so that the active material non-formation portions (protruding portions) of both electrode sheets protrude from both sides in the width direction. The wound body was crushed from the side to obtain a flat wound electrode body.
The positive electrode sheet constituting the positive electrode protruding portion of this electrode body is gathered in the radial direction (normal direction with respect to the flat surface) and one end of the aluminum positive electrode terminal is welded, and the negative electrode sheet constituting the negative electrode protruding portion is radially aligned. One end of a copper negative electrode terminal was welded together.

As the container, the length in the vertical direction (width direction of the flat wound electrode body) is 9.2 cm, the length in the horizontal direction (axial direction of the wound electrode body) is 11 cm, and the thickness is An aluminum container having a flat box shape with a length of 1.35 cm was used. The wound electrode body was accommodated in the container. In addition, in order to be able to measure the temperature of each part from the outside, thermocouples are respectively provided at one end (the end on the positive terminal side), the other end (the end on the negative terminal side), and the center of the container. Arranged. Into this container, an electrolytic solution containing lithium hexafluorophosphate (LiPF ₆ ) as a supporting salt in a mixed solvent of EC, DMC, and EMC at a concentration of about 1 mol / liter was injected, and then the container was sealed did. Thereafter, an initial charge / discharge treatment (conditioning) was performed by a conventional method to obtain a lithium ion battery having a theoretical capacity of 5 Ah.

  A charge / discharge pattern including a high rate discharge for 10 seconds at 150 A (corresponding to a discharge time rate of 30 C) is applied to the lithium ion battery obtained above, and the temperature change of each part due to this is detected by the thermocouple. Grasped from. More specifically, by applying the following charge / discharge patterns (1) to (4) in a room temperature (about 25 ° C.) environment, and comparing the temperature of each part before and after that, each part by the above charge / discharge pattern The temperature rise width of was determined.

[Charge / discharge pattern]
(1) Discharge at 150 A for 10 seconds.
(2) Pause for 5 seconds.
(3) CC-CV charge at 40 A for 120 seconds (constant voltage charge until constant charge is 120 seconds after constant current charge to 3.72 V at 40 A).
(4) Pause for 5 seconds.

  As a result, before and after the charge / discharge pattern (one cycle), the temperature rise at both ends of the battery was 1.2 ° C., whereas the temperature rise at the center was 2.2 ° C. That is, in the high-rate (rapid) charge / discharge pattern as described above, a clear temperature difference was generated between the both ends and the center of the battery even after only one high-rate discharge for 10 seconds. If the charge / discharge pattern continues further, the battery reaction (current) concentrates on the relatively hot spot, and as a result, more heat is generated at the hot spot, increasing the temperature difference once generated. Will be. For example, the temperature difference between the central portion and both end portions after the charge / discharge pattern was continuously repeated was increased to 7 ° C.

  A temperature distribution image in the axial direction of a lithium ion battery (having no heat radiating member inside the wound inner periphery of the electrode body) that generates the temperature distribution as described above by high-rate charge / discharge is shown by a two-dot chain line in FIG. . A one-dot chain line in the figure shows a case where a metal plate is arranged inside the wound inner periphery of the electrode body 80 (for example, when the metal plate 72 constituting the heat radiating plate 70 is used alone as a heat radiating member in the above embodiment). The temperature distribution image in is shown typically. As described above, a simple metal plate (the heat transferability from the electrode body to the heat radiating member (and hence the cooling efficiency) is equal in each part in the axial direction) as the heat radiating member disposed inside the wound inner periphery of the electrode body. When arranged, although the cooling efficiency in each part in the axial direction increases as compared with the battery not having the heat radiating member, a temperature difference still occurs between the both ends and the central part of the battery 20.

  On the other hand, according to the heat dissipation plate 70 of the present embodiment, the metal plate 72 made of a metal material having a relatively high thermal conductivity, and the resin sheets 72 and 74 made of a resin material having a lower thermal conductivity than the metal material. 7, and the ratio of the exposed area of the metal plate 72 is higher at the axially central portion of the electrode body 80 than at both ends, and is schematically shown by a solid line in FIG. As shown in the figure, while using a simple metal plate (dashed line) while efficiently lowering the temperature of the central part (downward arrow in the figure) compared to a configuration without a heat dissipation member (dashed line) In contrast, since the phenomenon in which both ends are too cold compared to the central portion is suppressed, the temperature difference between the central portion and both end portions can be effectively relaxed (temperature distribution is made gentle).

  As another effect that can be realized by arranging the heat radiation plate 70 inside the wound inner periphery of the electrode body 80 as described above, an effect of improving the shape maintaining property of the electrode body 80 can be cited. For example, the battery performance can be further stabilized by preventing the electrode body 80 from being crushed too much on the inner peripheral side. The improvement in the shape maintaining property of the electrode body 80 in this manner is advantageous from the viewpoint of workability during manufacturing. Another effect that can be realized by the heat radiating plate 70 having the above-described configuration is an effect as a cushion material that relaxes expansion / contraction of the electrode body 80 due to charge / discharge. That is, since the resin sheets 72 and 74 have cushioning properties as compared with the metal plate 72, the electrode sheet 80 has a more heat-dissipating member than the metal plate 72 disposed inside the wound inner periphery of the electrode body 80. Expansion and contraction can be alleviated better. As a result, it is possible to mitigate an event in which the electrolytic solution held in the electrode body 80 is pushed out of the electrode body due to the expansion and contraction.

  In the above description, the heat radiation plate 70 is described in which the high heat conduction portion is made of a metal material (metal plate 72) and the low heat conduction portion is made of a resin material (resin sheets 74 and 76). However, the configuration of the high heat conduction portion and the low heat conduction portion is described. The material is not limited to a combination of a metal material and a resin material. For example, the combination of the constituent materials of the high thermal conductivity portion and the low thermal conductivity portion may be resin materials or metal materials having different thermal conductivities. Alternatively, for example, a resin material such as polypropylene is used as a constituent material of the low heat conductive portion, and a composite material of the resin material and metal (for example, a resin material mixed with metal particles, metal fibers, etc.) as a constituent material of the high heat conductive portion. May be used. 3 to 6, the surface shape of the metal plate 72 is shown as a simple planar shape. For example, portions of the surface of the metal plate 72 corresponding to the openings 74A and 76A (exposed to the outside through the openings 74A and 76A). It is good also as a structure by which the convex part was formed in the part to carry out. As a result, the inner periphery of the electrode body 80 and the metal plate 72 can be brought into better contact with each other (the adhesiveness between the two is improved and the heat dissipation at the central portion of the electrode body 80 is further increased). It is preferable that the height of the convex portion is substantially equal to the thickness of the resin sheets 74 and 76. Forming such a convex portion is also advantageous from the viewpoint of facilitating alignment between the metal plate 72 and the resin sheets 74 and 76.

<Embodiment 2>
A preferred embodiment in which the present invention is applied to a lithium ion battery having a cylindrical wound electrode body will be described with reference to FIGS.
In the lithium ion battery 120 according to the present embodiment, a cylindrical electrode body 180 formed by winding a laminated sheet in which a separator sheet is sandwiched between positive and negative electrode sheets 182 and 184 is a suitable electrolyte (practical solution). In addition to the electrolytic solution similar to the first embodiment, the electrode body 180 is accommodated in a container 150 having a shape (here, a cylindrical shape) that can accommodate the electrode body 180. As shown in FIG. 9, a heat radiating member 170 is disposed at the center of winding of the electrode body 180. A positive electrode terminal 160 and a negative electrode terminal 162 that are electrically connected to the positive electrode sheet 182 and the negative electrode sheet 184 respectively protrude from the upper end surface and the lower end surface of the container 150.

  As shown in FIGS. 9 and 10, the heat dissipation member 170 in the present embodiment includes stepped cylindrical high heat conductive members 172 and 176 in which the large diameter portions 172A and 176A and the small diameter portions 172B and 176B are formed coaxially. The large-diameter portions 172A and 176A have a configuration in which an insulating layer 175 is sandwiched between them and are coaxially joined. A metal material can be preferably used as the constituent material of the high thermal conductive members 172 and 176, and a resin material can be preferably used as the constituent material of the insulating layer 175. Outer circumferences of portions of the small diameter portions 172B and 176B of the high heat conductive members 172 and 176 that follow the large diameter portions 172A and 176A are covered with tubular low heat conductive members 173 and 177, respectively. As a constituent material of the low heat conductive members 173 and 177, a resin material can be preferably adopted. The outer diameters of the low heat conducting members 173 and 177 are substantially the same as the outer diameters of the large diameter portions 172A and 176A of the high heat conducting members 172 and 176. The high heat conductive members 172 and 176 are also used as electrode terminals 160 and 162. That is, end portions of the small diameter portions 172B and 176B penetrate the container 150 and protrude outward.

  The electrode body 180 is formed by tightly winding the laminated sheet around the low heat conductive members 173 and 177 and the large diameter portions 172A and 176A exposed therebetween. Here, as in the first embodiment, the positive electrode sheet 182 and the negative electrode sheet 184 are overlapped with a slight shift in the width direction. Thus, at both ends in the axial direction of the electrode body 180, one end in the width direction of the positive electrode sheet 182 protrudes outward from the wound core portion 181 and one end in the width direction of the negative electrode sheet 184 is at the wound core portion. A portion that protrudes outward from 181 is formed. The protruding portion of the positive electrode sheet 182 is gathered toward the inner diameter side and joined to the outer periphery of the small diameter portion 172B of the high heat conductive member 172 (positive electrode terminal 160) made of, for example, aluminum. Similarly, the protruding portion of the negative electrode sheet 184 is gathered to the inner diameter side and joined to the outer periphery of the small diameter portion 174B of the copper high thermal conductivity member 174 (negative electrode terminal 162), for example. The joining of the electrode sheets 182 and 184 and the high thermal conductive members 172 and 176 can be performed by, for example, welding.

  According to the lithium ion battery 120 having such a configuration, the heat dissipation member 170 can be used to dissipate heat at the central portion of the electrode body 180 in the axial direction more efficiently than both end portions. That is, since the high heat conductive members 172 and 176 (large diameter portions 172A and 176A) are exposed to the outside in the portion of the heat dissipating member 170 arranged in the center portion in the axial direction and the center portion in the width direction of the electrode body 180, The heat of the electrode body 180 can be efficiently transferred to the high heat conductive members 172 and 176. Further, since the high heat conductive members 172 and 176 are continuous from the central portion to one end and the other end in the axial direction of the heat radiating member 170, the heat received from the electrode body 180 can be effectively dissipated to the outside. it can. On the other hand, at both ends in the axial direction of the electrode body 180, the outer circumferences of the high heat conductive members 172, 176 (small diameter portions 172B, 176B) are covered with the low heat conductive members 173, 177 (the inner circumference of the electrode body 180 and the high heat conduction member). 172 and 176 are separated from each other by the low thermal conductive members 173 and 177), the heat of the electrode body 180 is less likely to be transmitted to the high thermal conductive members 172 and 176 compared to the central portion. In other words, heat dissipation is suppressed at both ends in the axial direction of the electrode body 180 as compared with the central portion. Therefore, according to the battery 120 of the present embodiment, similarly to the battery 20 according to the first embodiment, the temperature difference between the central portion in the axial direction of the electrode body 180 and both end portions is effectively eliminated or alleviated even when the high rate is used. be able to.

  As mentioned above, although this invention was demonstrated in detail, the said embodiment is only an illustration and what changed and modified the above-mentioned specific example is included in the invention disclosed here. For example, the type of the battery is not limited to the above-described lithium ion battery, and the present invention can be applied to various secondary batteries having different electrode body constituent materials and electrolyte compositions.

  The battery according to the present invention can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Accordingly, as schematically shown in FIG. 11, the present invention is a vehicle (typically including a battery 20 (which may be in the form of an assembled battery formed by electrically connecting a plurality of batteries 20 in series)) as a power source. Is provided with an electric motor such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle.

1 is a perspective view showing a battery according to Embodiment 1. FIG. 3 is a side view showing members housed in a battery container according to Embodiment 1. FIG. 2 is an exploded perspective view showing a heat dissipation plate of the battery according to Embodiment 1. FIG. 4 is a perspective view showing a heat dissipation plate of the battery according to Embodiment 1. FIG. It is the VV sectional view taken on the line of FIG. It is the VI-VI sectional view taken on the line of FIG. It is explanatory drawing which shows typically the temperature distribution image with respect to the winding axis direction of a battery provided with a flat wound type electrode body. 6 is a perspective view showing a battery according to Embodiment 2. FIG. 6 is a cross-sectional view showing members housed in a battery container according to Embodiment 2. FIG. 6 is a perspective view showing a heat radiating member of a battery according to Embodiment 2. FIG. It is a side view which shows typically the vehicle (automobile) provided with the battery which concerns on this invention.

Explanation of symbols

1 Automobile (vehicle)
20, 120 Lithium ion battery 60, 160 Positive terminal 62, 162 Negative terminal 70 Heat dissipation plate (heat dissipation member)
72 Metal plate (high heat conduction member, high heat conduction part)
74,76 Resin sheet (low heat conduction member, low heat conduction part)
74A, 76A Opening 80, 180 Winding type electrode body (electrode body)
82,182 Positive electrode sheet 84,184 Negative electrode sheet 170 Heat dissipation member 172 High thermal conductivity member (high thermal conductivity part, positive electrode terminal)
173 Low heat conduction member (low heat conduction part)
175 Insulating layer 176 High thermal conductivity member (high thermal conductivity part, negative electrode terminal)
177 Low heat conduction member (low heat conduction part)

Claims (7)

An electrode body in which positive and negative electrode sheets are wound;
A heat dissipating member disposed inside the wound inner periphery of the electrode body,
The said heat radiating member is a secondary battery comprised so that the center part of the winding axis direction of the said electrode body may be thermally radiated more efficiently than both ends. The heat dissipating member includes a high heat conduction portion made of a material having a relatively high thermal conductivity, and a low heat conduction portion made of a material having a lower heat conductivity than the high heat conduction portion,
The high thermal conductivity portion is continuous from a portion of the heat radiating member disposed at a central portion in the axial direction of the electrode body to at least one end of the heat radiating member in the axial direction,
The low heat conduction part is provided so as to cover the high heat conduction part at a part of the outer surface of the heat dissipation member facing the inner periphery of the electrode body and to expose the high heat conduction part at the other part. The battery according to claim 1.   The heat dissipating member is configured such that the portion of the heat dissipating member that is disposed in the central portion of the electrode body in the axial direction has a higher area ratio at which the high heat conducting portion is exposed than the portions that are disposed at both ends. The battery according to claim 2.   The battery according to claim 2 or 3, comprising a flat electrode body in which the electrode sheet is wound flatly as the electrode body.   5. The battery according to claim 4, wherein the heat dissipation member has a configuration in which the high heat conductive portion and the low heat conductive portions disposed on both sides thereof are stacked in a thickness direction of the flat electrode body.   The battery according to any one of claims 1 to 5, wherein the battery is a lithium ion battery.   A vehicle comprising the battery according to any one of claims 1 to 6.

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